Diesel powered railroad locomotives are characterized by extremely large fuel tanks which typically hold three or four thousand gallons of diesel fuel. The tanks are usually located beneath the frame and between the trucks, and may extend the full width of the locomotive. The shape of the tanks is usually somewhat irregular to fit the space available and to accommodate other locomotive components.
Fuel tank gauges on locomotives are usually located on or adjacent the tanks themselves and are thus convenient to the fueling crew. The high cost of fuel has increased the importance of accurately gauging the fuel quantity in a locomotive tank, particularly in those situations in which a locomotive passes on a long haul run from the operating control of one railroad to that of another. Under such circumstances, the fuel quantity carried by the engine at the time of transfer is carefully recorded and the operating costs for the respective companies apportioned accordingly. An accurate, reliable and easily read fuel gauge for locomotive fuel tanks is, for such purposes, a necessity.
In older diesel locomotives, the fuel gauge comprised a sight glass similar to those employed with steam boilers. Such gauges were fragile and, if broken, resulted in fuel leakage until the breakage was discovered. Furthermore, the interior surface of the gauge glass after a period of use became coated with fuel oil and the actual fuel level was difficult to read.
A later development utilized the principal of the sight glass but comprised essentially a slot in the side of the tank into which a glass gauge plate was inserted by means of a suitable seal assembly. Gauges of this type typically extended along only a portion of the tank wall. Although such types of gauges were less subject to damage than those utilizing a totally exposed sight glass, nonetheless breakage could occur and the replacement of the gauge required the emptying of the tank and the expensive job of removing and replacing the seals and gauge glass. Furthermore, such gauges also become fouled with oil residue and the fuel level can be difficult to locate due to the flush mounting of the gauge glass.
Because of the difficulties in reading the conventional sight glass or gauge glass arrangement described, a refinement of the sight glass was developed which utilizes a transparent plastic rod to receive light from a flashlight to illuminate the gauge. Gradations along the column appear differently above and below the fuel level line to enhance the correct reading of the fuel level. A gauge of this type is shown, for example, in U.S. Pat. No. 2,514,570.
Another form of locomotive fuel gauge utilizes a float arm within the tank coupled by a gear linkage to a dial type meter mounted in a sealed assembly in the side of the tank. Such arrangements suffer the serious disadvantage of difficulty of repair, because of the internal mounting of the mechanism as well as the increased complexity of the gauge in contrast to the simpler sight glass type arrangement.
Still another type of gauge which if desired can be mounted remotely from the tank, utilizes an indicator liquid distinct from the tank liquid and senses the level of the tank liquid by application of a pressurized gas, usually air, which is directed through a tube and permitted to bubble into the tank contents at an outlet of the tube near the bottom of the tank. The pressure required to bubble air through this outlet, which pressure is proportional to the tank liquid level, is sensed by the remote meter carrying the indicator liquid, the gauge scale of which is calibrated to read the quantity of tank liquid.
Such a system, although widely used in many fields for tank level monitoring, is somewhat complex for locomotive service and suffers the disadvantage of requiring a source of pressurized gas as well as means for applying the gas pressure each time a reading is taken. The failure to apply the gas pressure or to apply sufficient pressure to bubble gas through the tank liquid could result in an erroneous reading of the tank contents.
From the foregoing brief description of the variety of locomotive fuel gauges presently in use, it can be understood that none of the present designs has been deemed sufficiently superior to cause the others to be regarded as outmoded.
It is accordingly a first object the present invention to provide a locomotive fuel gauge which provides an accurate and easily read indication of the fuel quantity in the tank.
Another object of the invention is to provide a gauge as described of a rugged, reliable and relatively simple construction which is economical to make and install.
A still further object of the invention is to provide a gauge as described which can be easily and quickly retrofitted to existing locomotives without any modification of locomotive fuel tanks.
Still another object of the invention is to provide a gauge as described which can be easily, quickly and inexpensively repaired if damaged without draining the tank.
Still another object of the invention is to provide a gauge as described which if damaged will result in only a negligible fuel loss, even if the damage is not discovered for a period of time.